This invention relates to a vehicle traction control system and more particularly to such a system which is adaptive to the road surface coefficient of friction to limit the drive wheel torque input in the event of excess wheel spin.
It is a common experience with automotive vehicles for excess wheel spin to occur during vehicle acceleration when the operator initiated engine output torque delivered to the driven wheels are such that the frictional forces between the tire and the road are overcome. While a small amount of spin between the tire and the road surface is necessary in order to achieve a driving force, excessive spin results in the reduction of effective driving force and the lateral stability of the vehicle.
Systems have been proposed to limit the torque input to the driven wheels for traction control. Typically, these systems limit spin when the spin value reaches a predetermined condition by controlling the wheel driving torque independent of the road surface condition. However, a reaction to a wheel spinning condition may enhance stability and/or operator comfort when accelerating on one road surface condition but not when accelerating on another road surface condition.
Consequently, it would be desirable to provide a traction control system that would tailor the control of the torque applied to the driven wheels to the particular road surface condition so as to enhance stability of the vehicle and provide a satisfactory performance over all road surface conditions.